#include <iostream>
#include <fstream>
#include <algorithm>
#include <climits>
#include <iomanip>

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct Point {
    double x, y;
    int index;
};

enum Orientation {
    COLINEAR,
    CLOCKWISE,
    COUNTER_CLOCKWISE
};

Orientation calculateOrientation(Point p1, Point p2, Point p3) {
    double det = (p2.x - p1.x) * (p3.y - p1.y) -
                 (p3.x - p1.x) * (p2.y - p1.y);

    if (det > 0) return CLOCKWISE;
    else if (det < 0) return COUNTER_CLOCKWISE;
    else return COLINEAR;
}

Point points[150], poligon[150];
int length, poligonLength;

void buildPoligonTop() {
    for (int i = 1; i < length; i++) {
        while (poligonLength >= 2 &&
                calculateOrientation(poligon[poligonLength - 2], poligon[poligonLength - 1], points[i]) != CLOCKWISE)
            poligonLength--;

        poligon[poligonLength++] = points[i];
    }
}

void buildPoligonBottom() {
    for (int i = length - 2; i >= 0; i--) {
        while (poligonLength >= 2 &&
                calculateOrientation(poligon[poligonLength - 2], poligon[poligonLength - 1], points[i]) != CLOCKWISE)
            poligonLength--;

        poligon[poligonLength++] = points[i];
    }
}

int main() {
    fout << fixed << setprecision(6);

    fin >> length;
    for (int i = 0; i < length; i++) {
        fin >> points[i].x >> points[i].y;
        points[i].index = i;
    }

    sort(points, points + length, [](Point p1, Point p2) {
        return p1.x == p2.x ? p1.y > p2.y : p1.x < p2.x;
    });

    poligon[poligonLength++] = points[0];

    buildPoligonTop();
    buildPoligonBottom();

    poligonLength--;

    int startIndex = 0, minim = INT_MAX;
    for (int i = 0; i < poligonLength; i++)
        if (poligon[i].index < minim) {
            minim = poligon[i].index;
            startIndex = i;
        }

    fout << poligonLength << "\n";

    for (int i = startIndex; i < poligonLength; i++)
        fout << poligon[i].x << " " << poligon[i].y << "\n";
    for (int i = 0; i < startIndex; i++)
        fout << poligon[i].x << " " << poligon[i].y << "\n";
}